Method and Device for Reading Digital Tatooing, Computer Software Package and Corresponding Storage Means

Abstract

The invention relates to a method of reading a watermark, of the type comprising a step of determining at least one watermarking message contained in a data set, possibly preceded by a step of determining at least one suite of parameters of a watermarking channel undergone by the data set, each suite of channel parameters comprising at least one channel parameter. The step of determining at least one watermarking message and / or the prior step of determining at least one suite of channel parameters comprises (comprise): an estimation phase, consisting in processing at least one batch of data comprising data of the data set, so as to obtain N estimated element(s), with N≧0; and a verification phase, consisting in validating or invalidating, in view of the entirety or of at least a subset of the data set, each estimated element. In the foregoing, each estimated element is an estimated watermarking message, in the case of the step of determining at least one watermarking message, and a suite of estimated-channel parameters, in the case of the prior step of determining at least one suite of channel parameters.

Description

1. FIELD OF THE INVENTION1.1 Context of the Invention[0001]The invention lies in the field of digital video watermarking.[0002]More precisely, the invention relates to a method of reading a watermark.[0003]The invention has numerous applications, such as for example the reading of watermarks on video file (of MPEG 2 type for example). It allows for example protection against film piracy by screen copying (“DVD screeners”), that is to say by illegal recording by filming a cinema screen.[0004]More generally, the present invention can apply in all cases where the data to be processed can be stored over a certain depth, so as to be able to rewind during the processing of these data.[0005]The invention can be applied to any type of support data (video, image, audio, text, 3D data, etc.).[0006]Moreover, the invention applies whatever the format of the support data: in the form of a stream (for example a video signal picked up on a television channel), in the form of a file, in the form of...

AI Technical Summary

Benefits of technology

[0045]More precisely, one of the objectives of the present invention, in at least one embodiment, is to provide a technique for reading a watermark which combines the advantages of exhaustive decoding and of incomplete decoding, while alleviating their respective drawbacks.

[0083]Advantageously, said estimation phase and / or said verification phase also allows (allow) a reliability measure to be obtained associated with at least one estimated element.

Problems solved by technology

However, the decoding is carried out image by image and does not take into account the globality of the video.

If a message with a significant number of bits is inserted, the procedure is no longer suitable since it requires an excessive number of operations (see below the considerations on exhaustive decoding).

Moreover, if the sequence is uploaded, or if it undergoes an attack by collusion (several users merge their watermarked sequences with different messages in the hope of scrambling the watermarks), the proposed detection procedure does not make it possible to decode the watermark correctly.

However, such an algorithm is not used in practice since it leads to extremely long calculation times as soon as k exceeds about ten bits.

Unfortunately, for most corrector codes, these algorithms are incomplete.

If the channel is very noisy, the rate of decoding of the watermark will also be very low.

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